"It should not be necessary for users of UE4 to purchase another product in order to code a form with which to use it. This is not mentioned as a pre-requisite in the sales documentation for UE4. "
Correct, which is why it is "not" necessary. Dreamweaver is perfectly capable of creating forms very easily without any additional extensions. UE aids with the more difficult task (for people who don't code) of creating the code to send the email using the contents of a form or recordset, doing exactly what it says on the tin (or the sales page in this case).